Both quality assurance and quality control in a construction project are aimed at ensuring quality of the final product - the building. Even though they are critical parts of a construction project's quality management program, professionals often use the two terms interchangeably or listed together as QA/QC in construction consulting companies’ service offerings.
However, Quality Assurance and Quality Control are distinctly different activities.
Why should anyone care about the difference? There are several reasons why.
Understanding the difference between QA and QC helps clarify the communication between project owners, contractors and other stakeholders. A good understanding helps project owners and managers build the right team of internal and third party construction quality consultants to meet the project's quality goals. Conversely, a poor understanding can lead to decisions to forgo one or the other, increasing the risks of construction defects and other claims down the road.
Both QA and QC are valuable practices to help ensure quality. It pays to determine what exactly quality is. Quality is a measure of excellence in relation to customer/user requirements.
A quality product or service is free from defects and significant variations. It is the result of a process that adheres to measurable and verifiable standards that achieve uniformity of output. Ensuring quality is a strategic measure in construction against unwanted results, like claims.
Quality Assurance (QA) is a set of planned and systematic activities which are laid out before a building project starts. The aim of this activity plan is to give confidence that quality requirements will be fulfilled. We can put it simply, like this:
Quality Assurance is planning to do the right things at the right time and the right way.
Quality Control are observation techniques and activities which aim to identify whether the final product actually fulfills customer requirements. Quality Control also identifies the need for corrective measures. In other, simpler, words:
Quality Control monitors work as it happens and ensures that the results satisfy the requirements specified.
Quality Assurance is about a plan. It is carried out before the construction project starts. Quality Assurance is a process that manages for quality. QA lists the processes, standards and policies that need to be carried out and ensures they are known to the people who need to know them.
The key elements of Quality Control are observation and activity. Even when you have the best plan and system in place (that’s what Quality Assurance does), you still need to monitor the work as it occurs to make sure the results are what you expect them to be (Quality Control domain). Quality Control verifies the quality of the output.
Quality Assurance and Quality Control are different, but complementary part of a larger concept – Quality Management. Achieving success in a building project requires both QA and QC. If either QA or QC are left out, an effective construction quality program can be crippled.
If you only lay out plans that define processes and procedures to be carried out (QA) but they aren't followed by anybody, its become little more than a paper making exercise. Those plans may be great however poor execution will lead to lots of rework, change orders, and mistakes slipping through, only to later become construction defects.
On the other hand, if your inspectors conduct testing and observations to check the quality (QC) without a plan, you can miss the whole picture. The project can end up with inspection gaps or lack of follow-ups, mistakes can go undocumented and unaddressed. The project managers wouldn’t be able to see underlying greater problems that needed timely addressing – creating failures to improve the general way of delivering the product.